<!--
 * @Author: jay
 * @Date: 2021-08-17 22:13:57
 * @LastEditTime: 2021-08-17 22:34:24
 * @LastEditors: Please set LastEditors
 * @Description: 圆圈
 * @FilePath: \Briup\Common\study\2-css\3-其他样式规则\5-circle.html
-->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>嵌套圆</title>
    <style>
        .outer , .inner{
            box-sizing: border-box;         /* width : padding + border + 内容*/
            border-radius: 50%;
        }
        
        .outer{
            width: 300px;
            height: 300px;
            border: 3px solid #ccc;
            margin: 0 auto;

            padding: 50px;            /* 使内圆变化 */
            transition: padding 2s;
        }
        .outer:hover{
            padding: 10px;
            
        }
        .outer .inner{
            width: 100%;
            height: 100%;
            border: 5px solid #ccc;
        }
    </style>
</head>
<body>
    <div class="outer">
        <div class="inner">

        </div>
    </div>
</body>
</html>